Archaic waterlines and loose soil have slowed the progress of MBTA contractors working on the massive renovation project at Ashmont Station, prompting T officials to push their anticipated re-opening date for the Mattapan High Speed Trolley line from summer to late fall of 2007. ?As with many projects, we encountered some unforeseen conditions,? said Lydia Rivera, a spokeswoman for the MBTA. ?We ran into some waterlines that weren?t charted, had to dig a little deeper to get a footing.? Construction on a new viaduct, the snaking concrete structure that allows trolleys to re-direct at Ashmont and head back toward Mattapan Square, is ongoing. Rivera said that legislative officials and community leaders in Ashmont and Mattapan had been briefed on the unforeseen delay. ?At first it was a little disappointing, but one thing that was good is they came out ahead of it,? said state Rep. Linda Dorcena Forry. The satellite bus service that has been operating since the trolley line closed in 2006 will continue until that service reopens.